Add fact-based-answers discipline to CLAUDE.md

[realmarcin]

Summary

• Adds a "Fact-based answers only" section to CLAUDE.md: never state a comparison, count, status, or historical claim without verifying it in the current conversation via a tool call.
• Direct human request, made after a separate session presented an unverified comparison as fact and had to redo the analysis.
• Companion to culturebotai-claw#128, which added the same discipline there. This version is adapted to CommunityMech: instead of the "downstream Mech checkout can lag origin/main" pitfall (specific to the orchestrator repo), it names this repo's own stale-tracker pitfall -- issue [P0-P2 tracker] Repository safety, test, documentation, CI, and packaging remediation #669's P0/P1/P2 checklist state changes as sub-issues land, so it should be re-fetched via gh issue view rather than cited from memory or an earlier turn.
• Doc-only change; no code, schema, or generated-artifact changes.

Test plan

• git status --short in the worktree confirmed only CLAUDE.md changed.
• Verified issue [P0-P2 tracker] Repository safety, test, documentation, CI, and packaging remediation #669 exists and its checklist is real (gh issue view 669) before citing it as the example.
• N/A: doc-only change, no code paths exercised.